Potential underreporting of energy intake in the Ontario Health Survey and its relationship with nutrient and food intakes.

This study investigated potential underreporting of energy intake in the 1990 Ontario Health Survey (OHS). Underreporting was higher in overweight individuals, Asian-born individuals, and respondents from urban areas. Intakes of underreporters were slightly closer to current dietary guidelines (less fat, more fruit and vegetables, fewer sweets). These results underline that caution is warranted when interpreting the association of dietary data with health outcomes.

Place of birth and dietary intake in Ontario. I. Energy, fat, cholesterol, carbohydrate, fiber, and alcohol.

BACKGROUND: The importance of dietary intake in the prevention of major health problems is acknowledged. Because of the impact of culture on food intake, this study investigated the relationship between place of birth and nutrient intake in Ontario, using data from the 1990 Ontario Health Survey. METHODS: Adults (age = 18) were categorized as non-immigrants (born in Canada; n = 29,458) or immigrants (born outside of Canada, classified by countries of birth; n = 7,158). Energy, fat, cholesterol, carbohydrate, and fiber intakes were examined, as well as alcohol consumption during the previous week. A companion article describes results for protein and selected micronutrients. Multiple linear and logistic regression analyses investigated the association of place of birth with nutrient intakes, adjusting for sociodemographic factors and ethnicity. RESULTS: Fat and carbohydrate intakes were strongly associated with place of birth, but cholesterol and fiber intakes were not. Immigrants, overall, were less likely than nonimmigrants to consume more fat (OR = 0.45, P < 0.0001), less carbohydrate (OR = 0.55, P < 0.0001), or more alcohol (OR = 0.64, P = 0.0004) than recommended. However, variations existed by country of birth. CONCLUSIONS: Immigrants were generally more likely to meet recommendation for fat and carbohydrate intakes than were nonimmigrants. These healthy eating behaviors need to be reinforced as part of health promotion.

Place of birth and dietary intake in Ontario. II. Protein and selected micronutrients.

BACKGROUND: Because of the importance of dietary intake on health, this study investigated the relationship between place of birth and nutrient intake in Ontario, using cross-sectional data from the 1990 Ontario Health Survey. METHODS: Adults (age = 18) were categorized as nonimmigrants (born in Canada; n = 29,458) or immigrants (born outside of Canada, classified by countries of birth; n = 7,158). Protein, calcium, iron, vitamin C, thiamin, riboflavin, and niacin intakes were studied (a companion article describes energy and other nutrient intakes). Multiple linear and logistic regression analyses investigated the association of place of birth with nutrient intakes, adjusting for sociodemographic factors and ethnicity. RESULTS: The proportions of subjects at an increased risk of "inadequate" nutrient intakes were relatively low. However, immigrants (particularly from Asian countries) were at a higher risk of inadequate intakes of protein (OR = 1.51, P = 0.001), calcium (OR = 1.41, P < 0.0001), and iron (OR = 1.44, P = 0.002) compared with nonimmigrants. Immigrants from various Asian countries were more likely to report inadequate thiamin, riboflavin, and niacin intakes. CONCLUSION: Some immigrants groups in Ontario display higher risks of inadequate protein and micronutrient intakes compared with nonimmigrants. More research on the nutritional status of these subgroups is needed to develop culturally sensitive health and nutrition promotion programs.

Predictors of dietary intake in Ontario seniors.

This study determined the independent association of 24 risk factors with dietary intake in community-living seniors. The study sample was 5,073 seniors for whom complete data were available from the 1990 Ontario Health Survey. Risk factors were items completed on an interviewer-administered health questionnaire. Diet Score, Mean Adequacy Ratio and energy were the diet outcomes derived from a self-administered food frequency questionnaire. The independent association of risk factors with these diet outcomes was assessed with multiple linear regression analyses. Factors that were consistently and positively associated with diet outcomes included: education, income, social support, perceived health status, belief in the nutrition/health link, dependence in walking and vision. Factors that were consistently and negatively associated with diet outcomes included: chewing status, dentition, hearing, level of happiness and body mass index. These results provide a basis for the development of a screening tool for the identification of "at risk" subgroups of seniors.

A randomized trial of a low fat high fibre diet in the recurrence of colorectal polyps. Toronto Polyp Prevention Group.

After polypectomy for adenomatous colorectal polyps, 201 persons were randomized to receive counselling on a diet low in fat (the lesser of 50 g/day or 20% of energy) and high in fibre (50 g/day) (LFHF), or to follow a normal western diet (ND), high in fat and low in fibre. After 12 months of counselling, fat consumption was about 25% of energy in the LFHF group and 33% in the ND group; fibre consumption was 35 g and 16 g respectively. After an average of two years of follow-up, an intention to treat analysis led to a ratio of cumulative incidence rates of 1.2 (95% CL 0.6-2.2) for recurrence of neoplastic polyps, a finding which suggests no significant difference between dietary groups over the period of observation. An exploratory analysis conducted among 142 persons with substantial diet counselling indicated a reduced risk of neoplastic polyp recurrence in women (RR = 0.5), associated with reduced concentrations of faecal bile acids while on the LFHF diet, but indicated an increased risk of recurrence in men (RR = 2.1), associated with increased faecal bile acids. Although a larger study would be needed to rule out the role of chance, these findings of gender-specific associations between diet counselling and both faecal bile acid concentrations and recurrence of colorectal neoplasia are consistent with recently published evidence of differences between genders.

Randomized trial of the effect of calcium supplementation on fecal risk factors for colorectal cancer.

Newmark et al. (J Natl Cancer Inst 1984; 72:1323-8) hypothesized that supplementation with calcium would decrease the concentration of bile acids in aqueous phase feces and that such a reduction would reduce the risk of malignant disease in the bowel. A randomized trial was therefore undertaken to examine the effects of calcium supplementation on fecal biochemistry. A total of 68 men between 40 and 60 years of age volunteered to participate after having been selected randomly from population lists in Scarborough, a city in the Toronto area, Ontario, Canada. Participants were randomly assigned to receive a daily supplement of 3 g of calcium carbonate or a sucrose placebo for a period of 1 week. Fecal samples were collected for 2 days prior to supplementation and for the last 2 days of supplementation. Records of all foods consumed were kept throughout the study period. The average concentration of total soluble bile acids fell in the placebo group (-11.2 g/ml) but increased slightly in the calcium group (1.4 g/ml). Similar patterns of change were observed for deoxycholic acid (placebo, -3.0 g/ml; calcium, 4.5 g/ml). The distribution of changes in total bile acids and deoxycholic acid differed between randomization groups at the 10 percent level of significance in univariate analysis. After adjustment for initial stool chemistry and initial levels and changes in nutrient intake, no reduction in fecal bile acid levels was observed in association with calcium supplementation. In fact, a statistically significant (p = 0.05) increase in deoxycholic acid concentration remained in the calcium supplemental group. Thus, this study was unable to support the hypothesis that calcium supplementation alters aqueous phase bile acids in the manner hypothesized to be consistent with protection from colorectal cancer.

Estimation of the amount of dietary starch available to different populations.

The daily per capita availability of dietary starch was estimated for 38 selected countries using food disappearance data from the FAO provisional food balance sheets (1972-1974 average); starch availability was also estimated for Canada from 1960 to 1987 using Agriculture Canada disappearance data. Total starch availability varies fourfold among the difference countries; the availability of different sources of starch vary up to 80-fold. Wheat and roots-tubers were the major sources of starch in countries with low total starch availability. Either corn and pulses, rice and pulses, or wheat and potatoes were the major sources of starch in those countries with high total starch availability. Starch availability in Canada, both total and by source, has been relatively constant over the 27 years examined. Slight increases in total starch and starch from cereals and pulses in 1987 will need to be followed to determine whether these represent the beginning of a real change in per capita starch availability.

A randomized trial of vitamins C and E in the prevention of recurrence of colorectal polyps.

Because supplements of vitamins C and E had been associated with reduction of fecal mutagen levels, a double-blind randomized trial was designed to examine the effects of these vitamins on the rate of recurrence of colorectal polyps, presumed precursors for colorectal cancer. Two hundred patients believed to be free of polyps after removal of at least one colorectal polyp were randomized to receive a supplement of 400 mg each of ascorbic acid and alpha-tocopherol, or a placebo. Fifteen patients had to be excluded because a review of pathology indicated that their polyps were not adenomatous. A second colonoscopic examination was planned after 2 yr of supplementation. One hundred thirty-seven people (75% of eligible subjects) completed the study; polyps were observed in the second colonoscopy in 41.4% of 70 subjects on vitamin supplements and in 50.7% of 67 subjects on placebos. After adjustment for differences between groups in demographic and dietary factors before study entry, the relative risk of polyp occurrence was 0.86, with 95% confidence limits from 0.51 to 1.45, in an analysis of 129 subjects with complete information on demographic and dietary factors who had completed the trial. Of the 48 patients who had not completed the study, 7 had died, 33 had not returned to their physician for an examination, and 8 had had a follow-up colonoscopy or sigmoidoscopy. Inclusion of the three polyps found in these eight examinations led to an estimate of relative risk of 0.86 (95% confidence limits, 0.51 to 1.43). The findings of this investigation suggest that any reduction in the rate of polyp recurrence associated with vitamin supplementation is small, and a larger study would be required to ensure that an effect of this size was not a chance finding.

Assessment of past diet in epidemiologic studies.

The reproducibility of recall of diet was examined for 44 men in Toronto, Ontario, Canada, by comparing estimates of consumption obtained from a dietary questionnaire in 1982 with estimates of consumption made by recalling the original diet at an interview conducted one year later in 1983. Estimates of average consumption obtained by recall were significantly lower than those originally reported for most foods and nutrients, but the magnitude of the differences was never greater than 20% of the original estimate. Correlations between individuals' levels of consumption were greater than 0.7 for nine of the 13 foods and nutrients studied. Current diet, assessed from two-day food records, was also associated with consumption originally reported for some nutrients. Fecal levels of hemicellulose were associated with fiber consumption originally reported and with current fiber consumption, and urine levels of 3-methylhistidine were associated with past meat consumption. The best prediction of past consumption of fiber and fat, however, was obtained from the recalled diet. No significant additional contribution to the prediction was made from estimates of current consumption or from biochemical measures.

Dietary fiber and cancer: a supplement for intervention studies.

Dietary fiber is one of several variables being considered in the study of the relationship between diet and cancer. Intervention trials in which dietary fiber is increased are the most direct way of assessing the possible role of fiber in this disease. Two dietary snack products have been developed for use in a fiber intervention study: the high-fiber snack (HFS), which supplies 23 g of dietary fiber per day (mostly from wheat bran) and the low-fiber product (LFS), which provides 3.5 g. Over a 12-week period, 28 volunteers consumed the HFS for 6 weeks and the LFS for 6 weeks. Compliance, as assessed by reports, through recovery of a riboflavin marker in the urine and fecal fiber analysis, was good. The only adverse effects reported were mild abdominal discomfort and gas. Serum ferritin and calcium decreased in some subjects, indicating a need to supplement the products with these essential minerals. Consumption of the snacks did not affect total energy intake or the intake of the nutrients monitored.

Diet and cancer prevention: separating fact from myth.

Public belief about the role of diet in cancer ranges from the opinion that cancer is genetically determined through to the idea that a specific diet will prevent all cancer. This article examines current knowledge about food additives, vitamins and nutritional pharmacology in relation to present knowledge of cancer incidence.

Estimation of per capita crude and dietary fiber supply in 38 countries.

Per capita availability of crude and dietary fiber was estimated from 1972-74 FAO Food Disappearance Tables and factors derived from data on the fiber composition of foods. Total dietary and crude fiber, as well as dietary fiber from total cereals, wheat, rice, maize, other cereals, roots and tubers, pulses, vegetables, and fruits, was calculated for 38 countries. Total dietary fiber correlated highly with total crude fiber (r = 0.92). Cereals were the major source of fiber for most countries. With a few exceptions the estimated total dietary fiber and dietary fiber from cereals appear to be in reasonable agreement with other values obtained by a variety of methods for a number of developed countries. The reasons for some of the discrepancies found and the need for additional, more precise information on dietary fiber intake are discussed.

Dietary factors in colon cancer: international relationships.

The relationship between dietary factors and mortality from colon cancer was explored by an analysis of the correlation between age-adjusted colon cancer death rates for men in 38 countries and estimates of the availability of a number of dietary components. Cereals were the only source of fiber found to be negatively associated with colon cancer mortality after adjustment for the availability of total or animal fats, or total or red meats, foods that were themselves positively associated with mortality. The estimate of dietary fiber from cereals was more closely associated with mortality than that of crude fiber. The previously postulated protective effects of vitamins C and A and of cruciferous vegetables were not supported by the international data; we found no evidence of a negative association between colon cancer mortality and availability of these dietary factors. The positive association previously reported between colon cancer and beer consumption disappeared following adjustment for animal fat.

Special foods.

Special foods include all foods that have been modified to meet either a real or perceived health need. They include enriched foods which are so readily available that they are generally no longer considered special foods. More recently, calorie-reduced, carbohydrate-reduced, low-fat, high fiber and other types of modified foods have been introduced to the market in response to several sets of dietary guidelines which recommend specific dietary changes for the general public. More specialized food products for people with prescribed diets or food allergies are not as readily available. The Specialty Food Shop in Toronto is attempting to supply both the need for very special foods and information for their use.

"Doctor, should I take vitamins?".

Ingestion of vitamin and mineral supplements is widespread in North America despite the fact that nutritional deficiencies are rare except among small groups with unusual or severely restricted food intakes. Recommended Nutrient Intakes (RNIs) for Canadians have recently been revised. These values can be used to assess individual food intakes when the correct procedures for collecting nutrient intake information and the critical difference between the RNIs and a patient's individual requirement for nutrients are understood. Some of the dangers of overconsumption of supplements and the myths which contribute to this misuse are examined.

'Doctor, how can I lose weight?'.

Millions of Canadians are trying to lose weight. According to the Metropolitan Life Insurance Company's recently released height and weight tables, some of them don't need to lose weight from a health standpoint. For those who would benefit from weight loss, a good program includes a balanced, low fat, high fiber diet; exercise; behavior modification and moral support. Few of the popular books and self-help groups offer all these essential components.

The effect of dietary ascorbic acid and alpha-tocopherol on fecal mutagenicity.

The effect of supplemental ascorbic acid and alpha-tocopherol on fecal mutagenicity was examined in 2 studies involving 20 healthy human donors aged 22-55 years. The vitamins were given at a dose of 400 mg daily each. The mutagen was extracted from individual frozen feces samples with dichloromethane, and assayed with Salmonella Typhimurium tester strain TA100 without microsomal activation. In the first study, with a single donor on a controlled diet, the fecal mutagenicity decreased (P less than 0.001) on treatment to 21% of control. In the second study, with 19 donors on free-choice diets, the mutagenicity in producers on treatment decreased (P less than 0.01) to 26% of control. Addition of ascorbic acid and alpha-tocopherol directly to feces led to no change in mutagenicity. Antioxidants in the diet may have a role in lowering the body's exposure to endogenously produced mutagens.